UPDATE: I changed from 3 stars to 1 because of RoomieMatch's extremely rude and unnecessary customer "service." That said, it is a legitimate service... But should you ever politely reach out with a legitimate need for assistance, prepared to be rudely berated and insulted. The person who runs this site comes off as either a troll or extremely inane, as they seem to lack basic reading comprehension skills. For example, I told them repeatedly that I had no issue in receiving emailed matches to my Gmail account, yet they kept insisting that I must have missed their emails due to my own incompetence. They actually told me that I needed to follow "Email 101," and repeatedly insulted my intelligence. Perhaps it's true that I'm stupid, since I handed over my money to them...
Regarding reviewers complaining about being "spammed" with multiple emails and not being able to view any online profiles, the site is quite upfront about the type of service it provides, and what to expect. Also, users only receive emails with prospective roommate details if you pay $20. If you don't pay, others who have will receive your info, but you won't receive anyone else's.
When I used the service two years ago, I got in touch with several potential roommates, and quickly found one. So two years later when I needed to find a roommate again, I naturally handed over my $20 to sign right back up. Unfortunately I made the mistake of using a Yahoo email account this time, which rejected RoomieMatch's emails without even first sending them to my spam folder. RoomieMatch suggested using Gmail instead and did process this change, but was shockingly rude in its correspondence. They actually said that they couldn't tell if I was "engaging in much hyperbole," when I simply reached out to let them know that I hadn't received any of my matches at the Yahoo address. Also, this time around, none of my matches were responsive. I ended up finding my new roommate using the marketplace on a popular social media site for free.
TLDR: The marketplace on a popular social media site is a much better (and free) option, without the rude customer "service." If you do decide to try RoomieMatch, do so using a Gmail account.